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"B" Regen Braking???

Discussion in 'Gen 2 Prius Main Forum' started by ladyinblack, Jul 20, 2006.

  1. ladyinblack

    ladyinblack New Member

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    O.K. you'all pat your selves on the back you have answered my questions better than anyone at Toyota. One more whats the "B" position and what is regen braking. When I asked the salesman at Toyota what the "B" was he told me that meant the brakes were charging? :rolleyes: I am confused. I am still waiting for the call that my car is in, and since you'all know so more than the salespeople I figured that I would bother to ask one more question. Sorry Female not blonde but don't understand regenarative braking???
     
    #1 ladyinblack, Jul 20, 2006
  2. efusco

    efusco Moderator Emeritus
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    "B" is for 'Engine Braking'--At any speed over 20mph or if the ICE is already running and you drop into B-mode the ICE will spin using the compression in the cylinders to help slow the car. Further, regenerative braking will increase over the amount that would normally be present during coasting.

    For example....
    You start down a long hill at 50mph. Foot off brake and gas. You will regenerate energy due to the backward spin of MG2 at a rate of around 15 amps. That charge will go to the battery.

    You realize that you're picking up speed and want to slow. You carefully depress the brake pedal. Regenerative braking will increase up to around 30-90 amps depending upon the amount of brake pressure you apply.

    After a bit you're holding your speed, but you're tired of holding the brake down. You push your shifter into B. The ICE noise and RPM increases significantly, regeneration at a rate of around 30-40 amps occurs, the combination of which usually allows you to completely remove your foot from the brake pedal, but less charge goes to the battery.

    There are really no other good/practical uses of B-mode though others will list how "they" use it. But overall you will lose on overall energy efficiency with it's use.
     
    #2 efusco, Jul 20, 2006
  3. tumbleweed

    tumbleweed Senior Member

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    A good question, no one knows that until they develop an interest in Hybrid cars. Here is a good essay by hobbit (who posts here) on the B mode which also covers quite a bit on regenerative braking.

    http://techno-fandom.org/~hobbit/cars/b-mode.html

    The short answer is the salesman was wrong, no surprise. Regenerative braking is what you get in D when you apply the brakes, it uses the large motor/generator to slow the car down and put that energy into the battery. Actually you get a little of that when you just take your foot off the accelerator. The brake pedal gives you a lot more, then if you brake harder it starts using the regular brakes also (which we usually call friction brakes here).

    The B mode also regenerates some energy as described above but what it mostly does is use the gas engine to help slow the car down. Kind of like the 2 or L position of a normal automatic transmission. You will not have a use for the B mode to often.
     
    #3 tumbleweed, Jul 20, 2006
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